1. Field of Invention
This invention relates to a turnbuckle and, in particular to a turnbuckle which has an unlimited degree of expansion and contraction, and which eliminates cable twisting.
2. Brief Statement of the Prior Art
Turnbuckles are commonly used to secure the ends of cables, rods or other members, with a variable tensioning capability. A turnbuckle has a central link having opposite ends which are internally threaded with opposite oriented threads which receive compatibly threaded shafts bearing distal clasps such as hooks or loops. Rotation of the link member thereby extends or contracts the threaded shafts in the assembly, thus providing for variable tensioning of cables, etc., which are secured by the distal clasps of the shaft members.
There are a number of shortcomings in the conventional turnbuckle. The turnbuckle is awkward and difficult to use since the distal ends of the shafts are commonly attached to cables and the like which do not rotationally restrain the shafts. Consequently, adjustment of the tension on the cables by advancing or retracting the shafts in the link member usually requires one to grasp the shaft members, immobilizing these members while rotating the link member. Alternatively, one rotates the link member and entire assembly until sufficient torsion is developed in the cables to restrain the shafts, permitting their rotational movement in their threaded engagement with the link member. Another disadvantage of the conventional turnbuckle is that it has only a limited degree of expansion and contraction. Commonly the shafts are coaxial and their maximum travel in the assembly is no greater than one half the length of the link member and, commonly less as the link member often has a center rib which obstructs the inward movement of the shafts. The conventional turnbuckle is also bulky with a heavy, cast link member.
It is an objective of this invention to provide a turnbuckle which can be readily expanded or contracted simply by rotation of the link;
It is also an objective of this invention to provide a turnbuckle with unlimited degree of extension and contraction;
It is likewise an objective of this invention to provide a turnbuckle mechanism which can be readily incorporated in linear motion mechanisms; and
It is an additional objective of this invention to provide a turnbuckle mechanism for synchronous reciprocal movement of two members.
It is a further objective of this invention to provide a turnbuckle which avoids twisting of cables.
This invention comprises a turnbuckle mechanism in which a central link is provided with internal right and left hand compatible threads and which receives, at its opposite ends, one of a pair of longitudinally split externally threaded shafts which are threaded in opposite directions. The shafts are coaxially received in the internally threaded bore of the link and have distal clasps such as hooks or loops for attachment of cables, or other members such as rods or chains.